This study evaluates school personnel perceptions, knowledge, and behaviors before and after a 36-hr training program designed to prepare early childhood school personnel for implementation of an after-school family preventive intervention for conduct problems. Participants were 40 female school personnel (22 professionals and 18 paraprofessionals). Research Findings: Participation and satisfaction with the training program were high. Before training, school personnel responded correctly to 53% to 66% of knowledge questions and indicated that they would be "somewhat comfortable to comfortable" in facilitating the after-school groups with families. Before training, professionals had greater knowledge than paraprofessionals; there was no difference in initial comfort level by professional status. Trainees made substantial gains in knowledge related to cognitive-behavioral strategies for preschoolers, program philosophy, and group facilitation skills, responding correctly to 69% to 77% of questions. These large effects on knowledge were not moderated by professional status. There were no significant changes in comfort level. Gains in knowledge in cognitive-behavioral strategies generalized over time (5 months) but not across contexts (into the classroom). Practice or Policy: This study provides preliminary evidence for the feasibility and potential efficacy of a training program to prepare early childhood school personnel to implement an after-school family preventive intervention for conduct problems. (Contains 2 tables and 1 figure.)